1. Field of the Invention
This invention relates to a supporting foundation for heavy machinery and, more specifically, this invention relates to a tub upon which a walking dragline excavator or the like is supported.
2. Description of the Prior Art
Walking mechanisms for limited relocation of heavy equipment, such as a dragline excavator or like heavy equipment, are well known. When the weight of machinery is excessive, it is impractical to transport the same by apparatus utilizing either wheels or tracks.
Typically the main frame of such machinery is rotatably supported on a circular support tub, which engages the underlying terrain. Extending forwardly of the main frame and supported thereon is a boom which carries an excavating shovel. The excavator is maneuvered by a pair of opposed spuds mounted on the sides of the main frame. A longitudinally extending terrain-engagable shoe is disposed at the lower end of each spud. The spuds are simultaneously raised and translated to effect translational movement of the machinery.
When the frame and tub are elevated by the walking mechanism, the tub, which is carried by a lifting pin attached to the frame, is suspended with its leading edge inclined upwardly from its trailing edge. As the machinery is moved, the tub's trailing edge is drawn along the terrain. Because of the concentration of weight along this edge, the tub must be reinforced to compensate for the resulting stress amplification.
Due to the magnitude of the force exerted by the trailing edge on the terrain, a substantial amount of earth is scraped off as the tub is moved, resulting in the accumulation of a mound of earth beneath the tub. This is undesirable since it results in a concentration of stress on the bottom of the tub which, when the tub is lowered, might exceed the tub's structural capacity.